The present invention relates to mechanical vibrator assemblies of the type in which a slackening or reduction in the speed of rotation of the driven shaft will cause the assembly to cease vibrating. For instance, in a concrete block manufacturing machine, the mold is vibrated after being filled with concrete to effect a densifying of the concrete material in the mold and thereafter the molded units are stripped from the mold and removed to a kiln. Conventionally, in such machinery, the vibration has been intermittent, rather than continuous, and the periods of vibration have been interrupted by periods of non-vibration to permit mold stripping and recharging of a cementitious molding material in measured amount to the mold.
I am aware that there have been proposals to utilize systems of this general type, and particularly a system which employs an eccentric shaft surrounded by a relatively rotatable counterbalancing barrel or drum to provide intermittent vibration. Generally, the system is of the type disclosed in U.S. Pat. Nos. 2,528,620; 2,673,651; 2,852,946; 3,625,974; 3,772,923; and 3,948,354.
One of the prime objects of the present invention is to provide a vibrator assembly which need utilize no eccentric shaft in its construction.
Another object of the invention is to provide an assembly of the character described which is of an extremely sensitive nature and in which, upon a slowing of the driven shaft, automatically and quickly, without utilizing return springs or the like, assumes a balanced orientation so that the vibration excitation of the body ceases.
While one use of the device has been mentioned, it is to be understood that the vibration assembly will find many uses in various machinery of the character wherein the vibration is to be automatically interrupted.